The morphogenesis of most carbonaceous microstructures that resemble microfossils in Archean (4-2.5 Ga old) rocks remains debated. The associated carbonaceous matter may even-in some cases-derive from abiotic organic molecules. Mineral growths associated with organic matter migration may mimic microbial cells, some anatomical features, and known microfossils-in particular those with simple spheroid shapes.Here, spheroid microstructures from a chert of the ca. 3.4 Ga Strelley Pool Formation (SPF) of the Pilbara Craton (Western Australia) were imaged and analyzed with a com-
The study of benthic foraminifera in a complex marine system, like the Marmara Sea, is a key for understanding the influence of environmental factors on foraminiferal species, density, assemblage composition, and shell construction. This kind of study is important for further extensive use of foraminifera-based investigation of water mass and sediment exchange between the eastern Mediterranean and Black Sea through the Marmara Sea. Based on proximal-distal transect from the southwest coast of the Erdek Bay to the top of canyon close to the North Anatolian Fault, this study aims at defining the geochemical conditions at the seafloor and identifying the sediment constraints that act upon agglutinated test construction for selected species (Eggerelloides scaber, Textularia agglutinans, Textularia sagittula, Textularia truncata and Textularia bocki). Grain size, mineralogical, and chemical analyses of their shells were investigated and confronted with the main geochemical conditions prevailing during deposition and within the sediment. Among grains used to construct the agglutinated foraminiferal tests from available grains, both grain size selection and sorting have been evidenced. This suggests that the mineralogical composition is related to the species and the sample localization within the basin. Our observations further suggest that bottom water conditions of the Marmara Sea do not have a significant influence on agglutinated foraminiferal shell development, which is primarily driven by sediment characteristics. Our results are thus transposable to other environments.
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